There is now considerable evidence that ethanol exerts its pharmacological effects by altering the physicochemical properties of biological membranes. Although ethanol does induce changes in membrane lipid composition, studies to relate these alterations to the development of behavioral tolerance to ethanol have been unsuccessful. In our preliminary studies we have demonstrated the accumulation of fatty acid ethyl esters (FAEE) in the liver and brain of mice undergoing chronic and acute ethanol treatment. Accumulation of unsaturated FAEEs especially linoleate seems to be related to the development of tolerance to ethanol in these animals. Tbe proposed study will investigate further the mechanisms leading to the formation and accumulation of FAEEs and their relationship to the development of tolerance to ethanol. To achieve this we will study the effect of acute and chronic ethanol treatment and ethanol withdrawal on: 1. The formation of FAEEs in brain subcellular fractions including synaptic membrane preparations; 2. The activities of a) fatty acid ethyl ester synthase b) phospholipase A2 and c) cholesterol ester hydrolase in brain subcellular fractions; 3. Fatty acid profile of acyl groups of phospholipids, cholesterol esters and free fatty acids of synaptic membranes; and 4. Membrane fluidity changes. Activation of these three enzymes seems to be essential elements for the observed accumulation of FAEEs in these tissues. The proposed study wifl yield important information as to the mechanism of FAEE accumulation and should lead to a better understanding of biochemical processes involved in the development of tolerance to ethanol. The long range plan would be to see ff these metabolites contribute to biochemical alterations involved in the pathogenesis of ethanol induced diseases and it could serve as a biochemical marker in diagnosing alcohol dependency.